Printer having document thickness compensating device

ABSTRACT

This invention relates to a document printer of the type utilizing a print element having a small print stroke, the printer being adapted to compensate for variations in the quality and thickness of the document being printed on. A document guide means or receiving chute is provided, one side of which is formed at least in part by a pair of substantially flat elongated surfaces which defines a print plane. The surfaces are spaced by a predetermined distance to form an elongated opening. An elongated platen, the width of which is greater than the predetermined distance between the elongated surfaces is mounted in a position directly opposite the elongated opening. When a print operation is not to be performed, the platen is positioned so as not to interact with a document in the chute. However, when a print operation is to be performed, the platen is moved to a position in which it clamps the document in the chute tightly against both of the elongated surfaces. The portion of the document adjacent the elongated opening is thus precisely positioned in the print plane regardless of document quality or thickness. The print element is mounted for movement along the elongated opening and is adapted, during a print operation, to selectively project through the opening to impact a document clamped against the elongated surfaces. To further compensate for variations in document thickness, the platen is mounted, at least in part, on a resilient element, such as a spring, which biases the platen toward the element. The resilient mounting of the platen assures substantially uniform pressure against the elongated surfaces regardless of document thickness. A document holding assembly is also provided which assembly includes a document receiving slot, a suitable element for clamping the document in the slot, and elements for providing controlled movement of the assembly to position the document for printing.

United States Patent [191 Kwan et al.

[ 1 Oct. 14, 1975 PRINTER HAVING DOCUMENT THICKNESS COMPENSATING DEVICE [73] Assignee: Bunker Ramo Corporation, Oak

Brook, 11].

[22] Filed: Jan. 14, 1974 [21] Appl. No.: 433,096

Related US. Application Data [63] Continuation of Ser. No. 249,856, May 3, 1972,

abandoned.

[52] US. Cl. 197/127 R; 197/1; 197/135 R; 197/149; 271/265; 235/61.9 R; 346/74 R [51] Int. Cl. B41J 11/20 [58] Field of Search 197/149, 133 R, 135 R, 197/1, 6.6, 127; 269/254 R, 254; 271/265,

266; 235/6l.9 R; 346/74 R [56] References Cited UNITED STATES PATENTS 2,012,320 8/1935 Racz 197/135 R 2,149,478 3/1939 Triner 101/93 C 2,283,804 5/1942 Grant et a1 101/297 2,820,539 1/1958 Raak 197/135 R 2,901,969 9/1959 Rabinow... 101/93 C 3,029,920 4/1962 Seifried l97/6.6

3,191,526 6/1965 Ross lOl/233 3,199,650 8/1965 Brown et a1... 101/93 C 3,324,827 6/1967 Powell et al. 269/254 R 3,368,701 2/1968 Copping et al. 271/265 3,592,311 7/1971 Chou et a1. 197/1 R 3,625,142 12/1971 Bresler 101/93 C FOREIGN PATENTS OR APPLICATIONS 242,388 1/1963 Australia 271/266 1,224,696 3/1971 United Kingdom l0l/93 C OTHER PUBLICATIONS Delapchier et al., Pass Book for Desk Printer, IBM Technical Disclosure Bulletin, Vol. 13, No. 8, (Jan. 1971), p. 2350.

W. Reichert, Pressure Device of a Printer With a Movable Print Head, l.B.M. Technical Disclosure Bulletin, Vol. 16, No. 12, 5/74, p. 4102.

.1. E. Drejza et al., Ribbon Compensating Interposer,

IBM. Technical Disclosure Bulletin, Vol. 15, No. 3, 8/72, p. 908.

Primary ExaminerJ. Reed Fisher Assistant ExaminerWilliam Pieprz Attorney, Agent, or FirmF. M. Arbuckle ABSTRACT This invention relates to a document printer of the type utilizing a print element having a small print stroke, the printer being adapted to compensate for variations in the quality and thickness of the document being printed on. A document guide means or receiving chute is provided, one side of which is formed at least in part by a pair of substantially flat elongated surfaces which defines a print plane. The surfaces are spaced by a predetermined distance to form an elongated opening. An elongated platen, the width of which is greater than the predetermined distance between the elongated surfaces is mounted in a position directly opposite the elongated opening. When a print operation is not to be performed, the platen is positioned so as not to interact with a document in the chute. However, when a print operation is to be performed, the platen is moved to a position in which it clamps the document in the chute tightly against both of the elongated surfaces. The portion of the document adjacent the elongated opening is thus precisely positioned in the print plane regardless of document quality or thickness. The print element is mounted for movement along the elongated opening and is adapted, during a print operation, to selectively project through the opening to impact a document clamped against the elongated surfaces. To further compensate for variations in document thickness, the platen is mounted, at least in part, on a resilient element, such as a spring, which biases the platen toward the element. The resilient mounting of the platen assures substantially uniform pressure against the elongated surfaces regardless of document thickness. A document holding assembly is also provided which assembly includes a document receiving slot, a suitable element for clamping the document in the slot, and elements for providing controlled movement of the assembly to position the document for printing.

17 Claims, 5 Drawing Figures U.S. Patent Oct. 14, 1975 Sheet 1 of4 3,912,068

XVI

IIUIIIIHHUI PRINTER HAVING DOCUMENT THICKNESS COMPENSATING DEVICE RELATED A PucA IoNs' This application is a continuation of our copending application Ser..No. 249,856; filed May 3, 1972, and now abandoned. I This invention relates to a device lizedwith a printer tov compensate for variations in thickness of the document to be printed on.

. BACKGROUND OF THE INvEN'IioN In order to' print on a document with most existing printers, the document must be brought into contact with a print element. The relative movement between the document and the print element required to bring them into contact may-be effected by.moving eitherthe print element, theplaten on which the document'is:

mounted, or both. Normally, .the movement or stroke of the element moved is substantially greater than the thickness of the document being printed on so that variations in 'the thickness of the document isnot a factor limiting the capability of the printer or the print quality.

To the extent that document thickness has been a.-factor, a certain amount of give has been provided in, for

length of this stroke. For example, some printers utilize as the'print element-a matrix of wires which are moved only five to forty-five thousandths of an inch during the printing of each character. On the average, these wires are moved from fifteen to twenty thousandths of an inch.

Heretofore, high speed printers of this type have been employed, for example, to generate print-outs of information from a data processor. In these applications, the document being printed on is of a single thickness and fairly good control of document quality and thickness can be maintained. However, when it is attempted to'utilize print elements of this type in, for example, the printer of a bank teller machine, the small stroke of the element becomes a problem. In such applications, the printer may be called upon to operate with a variety of different types of documents such as, for example, bank passbooks, checkbooks, installment payment books and the like. In addition to thevarious types and quality of documents, thicknesses will-vary depending on the page of the document'which is being printed on and, since the document may be subject to a substantial amount of handling prior to printing, the quality and thickness of the document may be further varied. The small stroke of the print element requires, however, that the document be in exact registration with a print surface regardless of document thickness or quality.

SUMMARY OF THE INv NITioN This invention therefore provides a printer adapted for performing'print operations on a document.- The printer has a document guide means or receiving chute with first'and second spaced apart sides. At least a portion of the first side of the chute is formed from a pair of substantially flat elongated surfaces included as part which may be uti-.

of a print defining means. The surfaces are in a common plane which is definedas the print planeand are spaced .by a predetermined distance to form an elongated opening. An elongated platen, the width of which is greater than said predetermined distance, is mounted adjacent to the second side of the chute in a position directly opposite from the elongated opening. A means is provided for acting upon the platen mounting means for moving the platen between a first position in which it does not interact with a document in the chute and a second position in which the platen clamps a document in the chute tightly against both of the elongated surfaces. The portion of the document adjacent the elongated opening is thus precisely positioned in the print plane. A print means is mounted for movement along the elongated opening and is adapted, during a print operation, to selectively project through the opening to impact a document clamped against the elongated surfaces. Control means are provided which areoperative to cause the means for moving the platen to move the platen to the second position only when a print-operation is to be performed, the control means being operative when the performance of a print operation has been completed for returning the platen to the first position. In order to further compensate for variations in document thickness (within a predetermined range of thickness), the means for mounting the platen includes means for resiliently biasing the platen toward the first side of the chute. This permits a document to be clamped against the elongatedsurface with substantially uniform pressure regardless of document thickness.

A'document holding assembly is also provided which assembly has a document receiving slot, a means for clamping a document in the slot, and a means for providing controlled movement of the assembly to position the document for printing.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment ofthe invention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cut-away side view of a bank printer device incorporating the document thickness compensating mechanism of this invention, showing the mechanism in an unoperated position.

FIG. 2 is an enlarged cut-away side view of a portion of the printer shown'in FIG. 1 including the document thickness compensation mechanism showing the mechanism in an operated position.

FIG. ,3 is a top view of a portion of the printer shown in FIG..2.

FIG; 4; is aschematic diagram of electrical control circuitry utilized with the printer shown in FIGS. 1-3.

FIG. 5 is -a flow diagram of the operation of the printer of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the figures, it is seen that the printer of this invention includes a chute 10 which is adapted to receive a document 12 to be printed on. For purposes of the discussion to follow, the document 12 will be asv sumed to be a bank passbook and the printer to be part of a bank teller terminal. The mouth and upper open portion of chute are defined by a pair of guides 11 and 13. A pair of elongated sensing gauge bars 14 and 16 extend below guide 13, the bars 14 and 16 being spaced toprovide an opening 18 therebetween into which a print head 20 projects. The flat elongated surfaces 15and l7 of the aforementioned bars 14 and 16 define both a side of chute 10 and the plane in which printing-occurs (the print plane) in the area adjacent opening 18. The space between head and the print plane is somewhat less than the stroke length of print wires (not shown) in the head (for example, 20 mils). Where an inked ribbon is required, it will fill part of this space. -While slot 18 is not visible in FIG. 3, it extends under bar 14 from left to right (as viewed in FIG. 3) for a distance at least equal to the maximum length of a line to be printed. This would normally be substantially equal to the width of the chute 10.

While the nature of print head 20 does not form part of the present invention, it will, for purposes of illustration, be assumed to be a matrix wire print head of a type now commercially available from a number of sources. A matrix wire print head ofthis type is described in US. Pat. No. 3,592,311, entitled Wire Printing Head issued to A. S. Chou et al. on July 13,

1971, and in US. Pat. No. 3,690,431, entitled Print Head Assembly Containing Solenoids" issued to R0- bert Howard on Sept. 12, 1972. Print head 20 is mounted on a carriage 22 which may be moved by a suitable drive mechanism in a direction from left to right as viewed in FIG. 3. The carriage may thus be moved to permit print head 20 to be utilized to record a line of characters on document 12. The mechanisms for moving carriage 22 and for controlling the printing of characters by head 20 may be of conventional design and do not form part of the present invention. A description of these elements will therefore not be provided.

A document inserted into chute 10 comes to rest in a holder assembly 24 for a passbook, which holder assembly is mounted for vertical movement on shaft 25. Holder assembly 24 is attached by a clamp 26 to a timing belt 28 which passes over idler pulleys 30 and engages pulley 32. Main pulley 32 is driven by hidirectional motor 34. The controls for motor 34 will be described shortly.

Holder assembly 24 has a document receiving slot 36 in which the lower end of the document may be clamped by the plunger 38 of hold solenoid 40. As will be seen shortly, hold solenoid 40 is activated in response to the detection of a document in chute 10 by a photo-detector 42.

The document thickness compensation mechanism of the invention includes a motor 44 which is connected by a shaft 46 to a gear 48. Gear 48 engages a smaller gear 50 mounted on shaft 52. Also mounted on shaft 52 is a cam 53 having distortions such as grooves 55 and 57 formed thereon and a pair of cams 54 which are normally positioned to have their low dwells in contact with corresponding cam follower rollers 56 (see FIGS. 1 and 3). A switch 59 is positioned to be closed when any portion of cam 53 except grooves 55 and 57 are adjacent to it. Each cam follower roller56 is attached by a pin 58 to a corresponding plunger mechanism 60. As may be best seen in FIG. 2, each plunger 60 is fitted in a cylinder 61 with a compression spring 62 being captivated between the plunger and the inside far end of the cylinder. Each plunger is attached for movement in the corresponding cylinder 61 by a pin 65 riding in a slot 67 in the plunger. A collar 69 having a flange 64 is screw fitted to the outside of each cylinder 61 at the end thereof adjacent roller 56. Each cylinder 61 is supported in a sleeve 71 mounted in a bracket 68. The brackets 68 are secured to the printer housing by screws 70. A compression spring 66 is captivated between end flange 64 and bracket 68. An elongated platen 74 extending the width of chute 10 is secured to projection 72 of cylinders 61 by screws or pins 76.

When the elements are positioned as shown in FIG. 1, platen 74 is out of chute 10 permitting document 12 to be inserted into the chute and easily moved therein. When the cam is rotated to a high dwell position, as shown in FIG. 2, the platen is moved forward into the chute pressing the document firmly against flat elongated surfaces 15 and 17 of bars 14 and 16, assuring that the document is in precise registration with the printing surface. Spring 62 is compressed by an amount which varies with the thickness of the document and thus serves to compensate for document thickness. Thus, both the position and the pressure on the document remains substantially uniform regardless of document thickness, provided the thickness of the document is within a predetermined range of thicknesses which the printer is designed to accept.

OPERATION Referring now to FIG. 5, it is seen that the first step in the operation, step 80, is to insert a passbook or other document 12 into chute 10. Just before the document enters holder slot 36, photo-detector 42 detects that the passbook is in the chute and generates an output on line 82 (FIG 4) which is applied as one input to AND gate 84. The signal on line 82 is also applied to pulse generator 86. The output from pulse generator 86 is applied to set flip-flop 88 to its ONE state. ONE-side output line 90 from flip-flop 88 is connected as the other input to AND gate 84. Output line 92 from AND gate 84 is connected to energize solenoid 40 causing plunger 38 to be driven into slot 36 to compress and hold .the document therein (step 94, FIG. 5). The time required for the energizing of pulse generator 86 and for the setting of flip-flop 88 is sufficient to assure that the document is in slot 36 before solenoid 40 is energized. So long as there is a document in chute l0 and flip-flop 88 remains set, solenoid 40 remains activated to permit movement of the document to be controlled and to prevent the document from being removed.

During step 96, the next step in the operation, the document is positioned, either manually or automatically, to bring the line which is to be printed on into a position opposite opening 18 and print head 20. With manual operation, motor 34 is disengaged from pulley 32 to permit the operator to move document 12 and holder 24 until the document is in the desired position. With automatic operation, the next line to be printed on is either automatically detected from the book or keyed in by the operator, and motor 34 is then operated in a manner which does not form part of the present invention to lower holder assembly 24 until the document is properly positioned.

Nother further happens during the operation until an indication is received that a print operation is to commence (step 98). The print indication may be obtained terminal or, where the printer is being used as an online computer terminal, from the processor when it has completed the processing of a transaction and is ready to record the transaction in a passbook or other document 12. The print signal is applied through line 100 (FIG. 4) and OR gate 102 to trigger single-shot multivibrator 104. Single-shot 104 generates a pulse which is applied through OR gate 105 to start motor 44 driving shaft 46 in the counterclockwise direction. Cam 53 rotates with shaft 46, moving the actuator of switch 59 out of groove 55, thus closing the switch. Switch 59 remains closed, permitting signal to be applied through OR gate 105 to keep motor 44 running until after 240 of rotation, groove 57 comes adjacent to the switch. Thus, in response to the print signal on line 100, motor 44 rotates gear 48 in the counterclockwise direction (as viewed in FIGS. 1 and 2) and thus rotates gear 50 and earns 54 two-thirds of arevolution in the counterclockwise direction. As cams 54 are rotated, followers 56 ride up to a high dwell on the cams forcing plungers 60, cylinders 62 and platen 74 all forward (step 106). As platen 74 moves forward into engagement with the document 12, spring 62 is compressed by an amount which varies with the thickness of the document.

Spring 62 is, however, strong enough so that it compresses the document, regardless of its thickness, and clamps it firmly, and under a substantially uniform pressure, against sensing bars 14 and 16, and thus against print plane defining surfaces 15 and 17 of the printing surface formed by opening 18. Spring 62 is preferably critically damped so as to provide a firm, vibrationand bounce-free platen for the document during the printoperation to follow.

When the document has been properly clamped by platen 74, carriage 22 starts to move (step 108) and the print operation begins (step 110). As indicated previously, the mechanisms and controls for these operations do not form part of the present invention and will not be described further herein.

When the print operation has been completed, a carriage return signal is generated (step 112), either in response to the manual depression of a carriage return key by the operator, or, with an on-line system, from a processor. The carriage return signal is applied through line 114 (FIG. 4) and OR gate 102 to again trigger single-shot-l04. This results in motor 44 again being started and in cams 53 and 54 being rotated through one-third revolution (120) in the clockwise direction until groove 55 is again adjacent switch 59. This permits followers 56 to return to the low dwell positions shown in FIG. 1. Plungers 60 and the elements attached thereto are returned to their normal positions shown in FIG. 1 by the action of cam follower springs 66 on flanges 64. Step 116 is in this manner completed.

Referring now to FIG. 5, it is seen that the next step in the operation, step 118, is to determine if the message is to continue on an additional line. If the message is to continue on a following line, the operation branches to step 120 during which a determination is made as to whether the last line of the document has been printed on. Assuming that the last line of the document has not been printed on, the system then branches to step 122 during which the position of holder assembly 24, and thus of the document, is indexed up one line position to permit printing on the next line. This is accomplished by applying a signal through index line 124 (FIG. 4) to passbook holder drive motor 34. The index pulse on line 124 may be obtained by the operator depressing an index key on his terminal, from the processor in an on-line system, or,

as shown in FIG. 4, by delaying the carriage return signal on line 114 in delay 126 by a sufficient time to permit step 1 16 to be completed and then applying this signal as the index input to motor 34. This procedure is acceptable since the performing of the indexing causes no harm even if step 1 18 or should indicate that indexing step 122 is not required.

From step 122, the operation returns to step 98 to cause a print signal to appear on line 100. As previously described, this results in cams 54 being rotated by twothirds of a revolution to again move platen 74 in position to clamp the document 12 against the printing surface. The printing of a new line is then performed in the manner previously indicated.

If, during step 118, a determination is made that the message is not to continue, or if during step 120 a determination is made that the last line of a page has been reached, the system branches to step 128. It should be noted that in an on-line system, it may be necessary to hold the message to be printed (step 130) when the last line of the page has been reached. During step 128 a long index pulse is generated, either under manual or processor control, on line 124 or on a return line 132 to passbook holder motor 84 causing the document holder assembly 24 to be returned to the home position shown in FIG. 1. A signal is then applied through line 134, either under manual or processor control, to the ZERO-side of flip-flop 88 to reset this flip-flop to its ZERO state. Since a signal no longer appears on line 90, AND gate 84' is deconditioned, de-energizing hold solenoid 40. Plunger 38 thus returns to the position shown in FIG. 1 (step 136) permitting the document to be removed from chute 10 (step 138). If the document is a passbook or a similar document and the message is to continue on a subsequent page, the page is turned during step 140 and the operation branches back to step 80 during which the document is reinserted into chute 10 to initiate another cycle of operation.

A printer having a document clamping and thickness compensating mechanism has thus been provided. While in the description above, plunger 60 has been operated in response to a motor and cam arrangement, it is apparent that this mechanism could also be operated by a solenoid in the manner illustrated for document holding solenoid 40. The mechanism shown in the figures is, however, preferred because of the superior force and rigidity which it is adapted to provide. The electrical control circuitry of FIG. 4 is also shown merely for purposes of illustration and other suitable control circuitry could be utilized. Thus while the invention has been particularly shown and described above with reference to a preferred embodiment, it will be apparent to those skilled in the art that the foregoing and other changes in form and details could be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. A printer for performing print operations on separate, flexible paper-like documents which may be multiple layered and may vary in thickness in accord with the number of layers therein on which different print operations are performed, comprising a. a document guide means having first and second spaced-apart sides for insertion of said document therebetween;

b. print plane defining means having a pair of substantially flat elongated surfaces which form at least a portion of the first side of said document guide means, said surfaces extending transverse to the direction of document insertion and being in a common plane which is defined as the print plane, and said surfaces being spaced by a predetermined distance to form an elongated opening therebetween;

c. an elongated platen extending the length of said elongated opening and having a flat front printing surface along the length thereof, the width of which is greater than said elongated opening;

d. platen mounting means for mounting said platen adjacent the second side of said document guide means in a position directly opposite said elongated opening on said first side;

e. platen position control means acting upon said platenmounting means for moving said platen between a first position at which it does not interact with flexible paper-like document in said document guide means and a second position in which the platen clamps and flattens said flexible paperlike document in said document guide means tightly against both of said elongated surfaces, positioning the flattened surface of said flexible paperlike document on which printing is to be performed in said print plane, whereby the printing surface of said document adjacent said elongated opening is precisely positioned and backed by said platen in said print plane;

f. control means coupled to said platen position control means operative to cause said platen position control means to move said platen to said second position only when a print operation is to be performed and to return said platen to said first position when a print operation has been completed; and

. a short stroke print means mounted for movement along the length of said elongated opening, said print means being adapted, during a print operation, to act through said elongated opening to impact and uniformly print indicia on said flexible paper-like document along the length of said elongated opening.

2. A printer of the type described in claim 1 including a document holding assembly having a document receiving slot therein positioned to receive documents inserted in said document guide means, detecting means for detecting the insertion of a document in said document guide means, means responsive to said detecting means for clamping said document in said document receiving slot, and means for providing controlled movement of said document holding assembly to position said document held therein along said elongated opening for printing thereon.

3. A printer of the type described in claim 2 wherein the means for clamping the document in said slot is a solenoid controlled plunger.

4. A printer of the type describied in claim 1 wherein said platen mounting means includes a plunger and a document compensation compression spring positioned between said plunger and said platen, said spring yielding when said flexible paper-like docoument is clamped against said elongated surfaces by said platen by an amount which varies with the thickness of said document.

5. A printer as claimed in claim 1 wherein said platen position control means includes a cam follower coupled to said platen, a cam having first and second surfaces of different height positioned to engage said cam follower, and cam positioning means operative when a print operation is not to be performed for positioning the first surface of said cam adjacent said cam follower and operative when a print operation is to be performed for positioning said second surface adjacent said cam follower, said platen being in its first position when the first surface of said cam is adjacent said cam follower and said platen being in said second position when the second surface of said cam is adjacent said cam follower.

6. A printer of the type described in claim 5 wherein said platen position control means includes means operative when said cam has been moved to position said first surface adjacent said cam follower for returning said platen to said first position.

7. A printer of the type described in claim 6 wherein said means returning said platen to said first position includes a compression spring normally biasing said platen mounting means toward said cam.

8. A printer as claimed in claim 5 wherein said cam positioning means includes a motor coupled to rotate said cam, means operative when a print operation is to begin or when a print operation has been completed for starting said motor, and means for stopping said motor when said first or second surface of said cam is adjacent said cam follower.

9. A printer as claimed in claim 1 wherein printing is to be performed on a selected surface of a document, said printer being adapted for printing on a single or multiple page document, the thicknesses of which may vary within a predetermined range; and wherein said platen mounting means includes means for resiliently biasing said platen toward said first side of said document guide means, whereby, when said platen is in said second position, a document is clamped flattened and backed by said platen against said elongated surfaces with substantially uniform pressure along the length of said document positioned along said elongated surfaces regardless of document thickness.

10. A printer as claimed in claim 1 wherein said print plane defining means includes a pair of elongated bars spaced by said predetermined distance, each of said bars having one of said flat, elongated surfaces as a surface thereof.

ll. A printer as claimed in claim 1 wherein said platen position control means for moving the platen includes a cam follower coupled to said platen near each end thereof, a cam positioned adjacent each of said cam followers, said cams each having first and second surfaces of different height, a common shaft on which both of said cams are mounted, and means for rotating said shaft to alter the cam surfaces which are adjacent said cam followers, said platen being in its first position when the first surface of each of said cams is adjacent the corresponding cam follower and said platen being in said second position when the second surface of each of said cams is adjacent the corresponding cam follower.

12. A printer of the type described in claim 1 wherein said short stroke print means comprises a wire print head of a type having a print stroke of 5 to 45 thousandths of an inch; and wherein said flat elongated surfaces are positioned such that said print plane is spaced from said print head by less than the length of said print stroke. l

13. A printer of the type described in claim 1 wherein said-short stroke print means comprises a plurality of printelements adapted to selectively project through said elongated opening to print indicia on said flexible paper-like document positioned in said print plane, the density of the indicia printed on said flexible paper-like document being a function of the spacing between the rest position of said print elements and the surface of said flexible paper-like document upon which the indicia are to be printed, the normal variations in the surface of said flexible paper-like document when unsupported in said print plane being in excess of that required for the uniform printing of indicia thereon by said short stroke print means. v

14. In a printer for printing multiple lines of characters on a document, said printer having a document guide means for guiding a document between a print element and a platen, a device for controlling the positioning of the document between said platen and said print element for printing thereon, comprising a. a document holding assembly having a document receiving slot adjacent one end of said document guide means for receiving a document inserted into the other end of said document guide means, said document holding assembly having an initial rest position with respect to said print element and said platen and is movable for positioning said document with a selected portion thereof in printing position opposite the printing element;

b. detecting means for detecting the insertion of a document in said document guide means for reception by said document holding assembly;

c. clamping means movable with said document holding assembly and responsive to said detecting means for clamping a document inserted in said document guide means in said slot;

. drive means operatively coupled to said document holding assembly for providing controlled movement of said document holding assembly to position a document clamped in said slot adjacent said print element and said platen for printing lines on said document; and

e. control means coupled to said drive means for indexing and moving said document with respect to said print element and said platen for each line to be printed thereon and to return said document holding assembly to its initial rest position and unclamping said document when the printing of all lines which are to be printed on said document has been completed.

15. The structure as claimed in claim 14 wherein said detecting means comprises a photoelectric detector.

16. A printer for performing the printing of one or more lines on a multi layered flexible paper-like document the thickness of which varies in accord with the number of layers therein, comprising a. a document guide means having first and second spaced-apart sides for receiving a flexible paperlike document on which a print operation is to be performed;

b. a document holding assembly having a document receiving slot positioned for receiving said document inserted into said document guide means, said document holding assembly having an initial position with respect to said document guide means;

c. detection means for detecting and generating an electrical output in response to the insertion of said document in said document guide means;

d. seizingmeans responsive to said electrical output from said detecting means for holding said document in said document holding assembly;

e. means for providing controlled movement of said document holding assembly to position said document held therein for the printing of each line thereon and for returning said document holding assembly to said initial position when the printing on said document has been completed;

f. print plane defining means having a pair of substantially flat elongated surfaces extending transverse to the direction of document insertion which form at least a portion of the first side of said document gtiide means, said surfaces being in a common plane which is defined as the print plane, and said surfaces being spaced by a predetermined distance to form an elongated opening therebetween;

g. an elongated platen the width of which is greater than said elongated opening;

h. means for mounting said platen adjacent the second side of said document guide means in a position directly opposite said elongated opening, said platen normally being positioned in a first position in which it does not interact with said flexible paper-like document inserted in said document guide means;

. platen position control means coupled to said platen and operative when a line is to be printed for moving said platen to a second position in which it clamps and backs said flexible paper-like document in said document guide means tightly against both of said elongated surfaces, whereby the portion of said document adjacent said elongated opening is flattened and precisely positioned in said print plane by said platen, said control means being operative to return said platen to said first position when the printing of a line is completed permitting said document to be repositioned by said means for providing controlled movement therefor;

j. control means coupled to said platen position control means operative to cause said platen position control means to move said platen to said second position only when a print operation is to be performed and to return said platen to said first position when a print operation has been completed, and

. a short stroke print means mounted for movement along said elongated opening, said print means being adapted, during the printing of a line, to act through said opening to impact a document clamped against said elongated surfaces by said platen.

17. A printer for performing print operations on a flexible paper-like document comprising a. a document guide means having first and second spaced-apart sides;

b. print plane defining means having a pair of substantially flat elongated surfaces which form at least a portion of the first side of said document guide means, said surfaces being in a common plane which is defined as the print plane, and said surfaces being spaced by a predetermined distance to form an elongated opening therebetween;

c. an elongated platen the width of which is greater than said elongated opening;

d. platen mounting means for mounting said platen adjacent the second side of said document guide means in a position directly opposite said elongated opening;

. platen position control means having a cam folsaid second surface of said cam adjacent said cam follower thereby positioning said platen in a second position in which said platen clamps and flattens said document in said document guide means tightly against both of said elongated surfaces placing said document in said print plane; and

' control cam coupled to said positioning means so as to be moved thereby, and a cam controlled switch positioned adjacent said control cam, the surface of said control cam having a pair of distortions formed therein at positions such that said switch is adjacent a distortion only when said control cam is positioned to maintain said platen in ei ther its first position or its second position, said switch being operative to energize said cam positioning means when said switch is not adjacent a UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 1 3 912 068 DATED October 14, 1975 INVENTOR(S) OkunKwan and James John Boyce H is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 17, cancel "counter".

Signed and Sealed this seventeenth D3) Of February 1976 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner oj'lalenrs and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION P PATENT NO. 3,912 0 DATED October 14, 1975 lNVENTORtS) OkunKwan and James John Boyce It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 5, line 17, cancel "counter-".

5 Signed and Scaled this seventeenth D ay Of February 1976 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Parents and Trademarks 

1. A printer for performing print operations on separate, flexible paper-like documents which may be multiple layered and may vary in thickness in accord with the number of layers therein on which different print operations are performed, comprising a. a document guide means having first and second spaced-apart sides for insertion of said document therebetween; b. print plane defining means having a pair of substantially flAt elongated surfaces which form at least a portion of the first side of said document guide means, said surfaces extending transverse to the direction of document insertion and being in a common plane which is defined as the print plane, and said surfaces being spaced by a predetermined distance to form an elongated opening therebetween; c. an elongated platen extending the length of said elongated opening and having a flat front printing surface along the length thereof, the width of which is greater than said elongated opening; d. platen mounting means for mounting said platen adjacent the second side of said document guide means in a position directly opposite said elongated opening on said first side; e. platen position control means acting upon said platen mounting means for moving said platen between a first position at which it does not interact with a flexible paper-like document in said document guide means and a second position in which the platen clamps and flattens said flexible paper-like document in said document guide means tightly against both of said elongated surfaces, positioning the flattened surface of said flexible paperlike document on which printing is to be performed in said print plane, whereby the printing surface of said document adjacent said elongated opening is precisely positioned and backed by said platen in said print plane; f. control means coupled to said platen position control means operative to cause said platen position control means to move said platen to said second position only when a print operation is to be performed and to return said platen to said first position when a print operation has been completed; and g. a short stroke print means mounted for movement along the length of said elongated opening, said print means being adapted, during a print operation, to act through said elongated opening to impact and uniformly print indicia on said flexible paper-like document along the length of said elongated opening.
 2. A printer of the type described in claim 1 including a document holding assembly having a document receiving slot therein positioned to receive documents inserted in said document guide means, detecting means for detecting the insertion of a document in said document guide means, means responsive to said detecting means for clamping said document in said document receiving slot, and means for providing controlled movement of said document holding assembly to position said document held therein along said elongated opening for printing thereon.
 3. A printer of the type described in claim 2 wherein the means for clamping the document in said slot is a solenoid controlled plunger.
 4. A printer of the type describied in claim 1 wherein said platen mounting means includes a plunger and a document compensation compression spring positioned between said plunger and said platen, said spring yielding when said flexible paper-like docoument is clamped against said elongated surfaces by said platen by an amount which varies with the thickness of said document.
 5. A printer as claimed in claim 1 wherein said platen position control means includes a cam follower coupled to said platen, a cam having first and second surfaces of different height positioned to engage said cam follower, and cam positioning means operative when a print operation is not to be performed for positioning the first surface of said cam adjacent said cam follower and operative when a print operation is to be performed for positioning said second surface adjacent said cam follower, said platen being in its first position when the first surface of said cam is adjacent said cam follower and said platen being in said second position when the second surface of said cam is adjacent said cam follower.
 6. A printer of the type described in claim 5 wherein said platen position control means includes means operative when said cam has been moved to position said first surface adjacent said cam follower for returning said platen to said first position.
 7. A printer of the type described in claim 6 wherein said means returning said platen to said first position includes a compression spring normally biasing said platen mounting means toward said cam.
 8. A printer as claimed in claim 5 wherein said cam positioning means includes a motor coupled to rotate said cam, means operative when a print operation is to begin or when a print operation has been completed for starting said motor, and means for stopping said motor when said first or second surface of said cam is adjacent said cam follower.
 9. A printer as claimed in claim 1 wherein printing is to be performed on a selected surface of a document, said printer being adapted for printing on a single or multiple page document, the thicknesses of which may vary within a predetermined range; and wherein said platen mounting means includes means for resiliently biasing said platen toward said first side of said document guide means, whereby, when said platen is in said second position, a document is clamped flattened and backed by said platen against said elongated surfaces with substantially uniform pressure along the length of said document positioned along said elongated surfaces regardless of document thickness.
 10. A printer as claimed in claim 1 wherein said print plane defining means includes a pair of elongated bars spaced by said predetermined distance, each of said bars having one of said flat, elongated surfaces as a surface thereof.
 11. A printer as claimed in claim 1 wherein said platen position control means for moving the platen includes a cam follower coupled to said platen near each end thereof, a cam positioned adjacent each of said cam followers, said cams each having first and second surfaces of different height, a common shaft on which both of said cams are mounted, and means for rotating said shaft to alter the cam surfaces which are adjacent said cam followers, said platen being in its first position when the first surface of each of said cams is adjacent the corresponding cam follower and said platen being in said second position when the second surface of each of said cams is adjacent the corresponding cam follower.
 12. A printer of the type described in claim 1 wherein said short stroke print means comprises a wire print head of a type having a print stroke of 5 to 45 thousandths of an inch; and wherein said flat elongated surfaces are positioned such that said print plane is spaced from said print head by less than the length of said print stroke.
 13. A printer of the type described in claim 1 wherein said short stroke print means comprises a plurality of print elements adapted to selectively project through said elongated opening to print indicia on said flexible paper-like document positioned in said print plane, the density of the indicia printed on said flexible paper-like document being a function of the spacing between the rest position of said print elements and the surface of said flexible paper-like document upon which the indicia are to be printed, the normal variations in the surface of said flexible paper-like document when unsupported in said print plane being in excess of that required for the uniform printing of indicia thereon by said short stroke print means.
 14. In a printer for printing multiple lines of characters on a document, said printer having a document guide means for guiding a document between a print element and a platen, a device for controlling the positioning of the document between said platen and said print element for printing thereon, comprising a. a document holding assembly having a document receiving slot adjacent one end of said document guide means for receiving a document inserted into the other end of said document guide means, said document holding assembly having an initial rest position with respect to said print element and said platen and is movable for positioning said document with a selected portion thereof in printing position oppOsite the printing element; b. detecting means for detecting the insertion of a document in said document guide means for reception by said document holding assembly; c. clamping means movable with said document holding assembly and responsive to said detecting means for clamping a document inserted in said document guide means in said slot; d. drive means operatively coupled to said document holding assembly for providing controlled movement of said document holding assembly to position a document clamped in said slot adjacent said print element and said platen for printing lines on said document; and e. control means coupled to said drive means for indexing and moving said document with respect to said print element and said platen for each line to be printed thereon and to return said document holding assembly to its initial rest position and unclamping said document when the printing of all lines which are to be printed on said document has been completed.
 15. The structure as claimed in claim 14 wherein said detecting means comprises a photoelectric detector.
 16. A printer for performing the printing of one or more lines on a multi layered flexible paper-like document the thickness of which varies in accord with the number of layers therein, comprising a. a document guide means having first and second spaced-apart sides for receiving a flexible paper-like document on which a print operation is to be performed; b. a document holding assembly having a document receiving slot positioned for receiving said document inserted into said document guide means, said document holding assembly having an initial position with respect to said document guide means; c. detection means for detecting and generating an electrical output in response to the insertion of said document in said document guide means; d. seizing means responsive to said electrical output from said detecting means for holding said document in said document holding assembly; e. means for providing controlled movement of said document holding assembly to position said document held therein for the printing of each line thereon and for returning said document holding assembly to said initial position when the printing on said document has been completed; f. print plane defining means having a pair of substantially flat elongated surfaces extending transverse to the direction of document insertion which form at least a portion of the first side of said document guide means, said surfaces being in a common plane which is defined as the print plane, and said surfaces being spaced by a predetermined distance to form an elongated opening therebetween; g. an elongated platen the width of which is greater than said elongated opening; h. means for mounting said platen adjacent the second side of said document guide means in a position directly opposite said elongated opening, said platen normally being positioned in a first position in which it does not interact with said flexible paper-like document inserted in said document guide means; i. platen position control means coupled to said platen and operative when a line is to be printed for moving said platen to a second position in which it clamps and backs said flexible paper-like document in said document guide means tightly against both of said elongated surfaces, whereby the portion of said document adjacent said elongated opening is flattened and precisely positioned in said print plane by said platen, said control means being operative to return said platen to said first position when the printing of a line is completed permitting said document to be repositioned by said means for providing controlled movement therefor; j. control means coupled to said platen position control means operative to cause said platen position control means to move said platen to said second position only when a print operation is to be performed and to return said platen to said first position when a print operation has bEen completed, and k. a short stroke print means mounted for movement along said elongated opening, said print means being adapted, during the printing of a line, to act through said opening to impact a document clamped against said elongated surfaces by said platen.
 17. A printer for performing print operations on a flexible paper-like document comprising a. a document guide means having first and second spaced-apart sides; b. print plane defining means having a pair of substantially flat elongated surfaces which form at least a portion of the first side of said document guide means, said surfaces being in a common plane which is defined as the print plane, and said surfaces being spaced by a predetermined distance to form an elongated opening therebetween; c. an elongated platen the width of which is greater than said elongated opening; d. platen mounting means for mounting said platen adjacent the second side of said document guide means in a position directly opposite said elongated opening; e. platen position control means having a cam follower coupled to said platen, a cam having first and second surfaces of different heights positioned to engage said cam follower, cam positioning means operative when a print operation is not to be performed for positioning said first surface of said cam adjacent said cam follower thereby positioning said platen in a first position at which it does not interact with said document in said document guide means, said cam positioning means operative when a print operation is to be performed for positioning said second surface of said cam adjacent said cam follower thereby positioning said platen in a second position in which said platen clamps and flattens said document in said document guide means tightly against both of said elongated surfaces placing said document in said print plane; and f. a control cam coupled to said positioning means so as to be moved thereby, and a cam controlled switch positioned adjacent said control cam, the surface of said control cam having a pair of distortions formed therein at positions such that said switch is adjacent a distortion only when said control cam is positioned to maintain said platen in either its first position or its second position, said switch being operative to energize said cam positioning means when said switch is not adjacent a distortion. 